fix(sitestream): deathwatch resets live-cache liveness on aggregator termination (plan R2-07 T10)

src/ZB.MOM.WW.ScadaBridge.Communication/ISiteAlarmLiveCache.cs

@@ -60,6 +60,6 @@ public interface ISiteAlarmLiveCache
     /// cache is authoritative.
     /// </summary>
     /// <param name="siteId">The numeric site id.</param>
-    /// <returns><c>true</c> once the site's aggregator has seeded and published at least once.</returns>
+    /// <returns><c>true</c> while a <b>living</b> aggregator has seeded and published; reverts to false if the aggregator terminates (R2 N6) — a frozen snapshot is never reported as live.</returns>
     bool IsLive(int siteId);
 }